Cold extrusion forming die for tube blank forming special-shaped inner spline shaft

Abstract

The utility model discloses a pipe blank forming special-shaped internal spline shaft cold extrusion forming die which comprises an upper die and a lower die which are coaxially installed, a blank is placed in a concave die cavity of the special-shaped internal spline cold extrusion die, and an oil press moves downwards to drive a tooth punch to extrude the blank to obtain a special-shaped internal spline shaft. And the lower ejector rod moves upwards to eject the special-shaped inner spline shaft out of the female die cavity. The special-shaped internal spline is subjected to cold extrusion through oil press equipment, the overall cost is reduced, the straightness of the extruded special-shaped internal spline is the same as that of radial forging, the tooth profile mechanical strength is improved, and the production efficiency is high.

Description

Technical Field

[0001] The utility model relates to the field of mechanical manufacturing and processing equipment, in particular to a cold extrusion forming die for forming a tube blank with a special-shaped internal spline shaft. Background Art

[0002] Spline shafts are usually used in aircraft, automobiles, tractors, machine tool manufacturing, agricultural machinery and general mechanical transmission devices. Since spline shafts have multiple teeth, they have high load-bearing capacity, good centering and guiding properties, and their shallow tooth roots can reduce stress concentration.

[0003] Spline is a kind of mechanical transmission. It has the same function as flat key, semicircular key and oblique key, which are all used to transmit mechanical torque. There are longitudinal keyways on the surface of the shaft, and the rotating parts on the shaft also have corresponding keyways, which can keep rotating synchronously with the shaft. While rotating, some can also slide longitudinally on the shaft, such as the gear shift gear of the transmission. Spline shafts are mostly used in brakes and steering mechanisms. There is also a retractable shaft, which consists of inner and outer tubes. The outer tube has inner teeth and the inner tube has outer teeth, which are sleeved together. When in use, it can be retracted in the length direction while transmitting the rotational torque. The spline connection is a connection composed of a shaft and a hub with multiple longitudinal key teeth; it corresponds to the external spline and the internal spline.

[0004] The spline shaft in the prior art is formed by radial forging, such as a method for forming a cast tooth profile and a molded product disclosed in Japanese patent JP2012196695A, by placing a rough material in a mold and then pressing a spline punch into the rough material to mold a spline bearing in the inner peripheral portion of a pulley. The clearance groove is formed in the material in advance and is adjacent to the spline hole formed by the spline bearing. When forging, the axial ends of the spline hole are maintained to allow the plastically flowing material to flow into the clearance groove, so that the spline bearing and its two ends can be molded with high dimensional accuracy, while preventing the internal pressure of the mold from rising excessively, thereby eliminating the machining after forging. Since radial forging is all imported equipment, the structure is complex, the specificity is strong, the price is expensive, and the cost is relatively high.

[0005] Another example is Chinese patent CN 105013844 A which discloses an internal spline cold extrusion device for an automobile steering pump shaft, which is composed of a hydraulic press and a mold, wherein the mold includes an upper mold and a lower mold, wherein the upper mold is mounted on the upper working platform of the hydraulic press, and an internal spline punch matching the inner hole of the part is mounted below the upper mold, and the lower mold is mounted on the lower working platform of the hydraulic press, and a mold cavity matching the outer circle of the part is opened at the center of the lower mold, and the centers of the internal spline punch and the mold cavity are on the same straight line. Through the above manner, the present invention has a simple structure, is easy to operate, can save raw materials, and reduce production costs, and can also improve the coaxiality of the internal spline and the outer circle of the part, saving a lot of time for the subsequent extrusion of the external spline and improving work efficiency. Utility Model Content

[0006] Purpose of the utility model: The purpose of the utility model is to solve the deficiencies of the prior art and to provide a cold extrusion forming die for forming a special-shaped internal spline shaft of a tube blank. By adopting a hydraulic press to cold extrude the special-shaped internal spline, the cost is reduced. The straightness of the extruded special-shaped internal spline is the same as that of the radial forging, the mechanical strength of the tooth profile is improved, and the production efficiency is high.

[0007] Technical solution: In order to achieve the above purpose, the utility model discloses a cold extrusion forming die for forming a special-shaped internal spline shaft of a tube blank, comprising an upper die and a lower die coaxially installed, the blank is placed in a concave mold cavity of the special-shaped internal spline cold extrusion die, and the oil press is used to move downward to drive the tooth punch to extrude the blank to obtain the special-shaped internal spline shaft, and the lower ejector rod moves upward to eject the special-shaped internal spline shaft from the concave mold cavity;

[0008] The upper die comprises: a punch sleeve, an outer punch transition sleeve, an outer punch, a tooth punch transition sleeve, a tooth punch, a punch pad, an upper template, an upper locking nut and an upper die barrel, wherein the punch pad is installed in the punch sleeve, the outer punch sleeve is arranged on the outer side of the tooth punch, the end of the tooth punch is fixed in the punch sleeve through the tooth punch transition sleeve, the end of the outer punch is fixed to the punch sleeve through the outer punch transition sleeve, the punch sleeve is fixed to the upper template through the upper die barrel, and the upper locking nut sleeve provided on one side of the axial direction of the upper die barrel is arranged on the punch sleeve;

[0009] The lower die comprises: a three-layer stress sleeve structure obtained by coaxially arranged and sequentially close die A, die B, and die C, a die sleeve sleeved on the radially outer sides of die A, die B, and die C, the die sleeve being fixed on a die pad located on the axial end faces of the die sleeve and die C by a pressing plate, a lower die barrel being sleeved on the radially outer sides of the die sleeve and die pad, a lower locking nut being sleeved on the radially outer sides of the lower die barrel, the lower die barrel being vertically fixed on the lower template, and a lower ejector rod being passed through the die pad and the lower template.

[0010] As a further preferred embodiment of the present invention, in step 2, the deformation of the blank is controlled within 60%, and the punch unit pressure does not exceed 2500Mpa. The deformation of the tooth extrusion is mainly limited by the radial size of the outer circle of the blank. By adjusting the radial size of the outer circle of the blank, the deformation of the tooth extrusion is adjusted. The inner hole size of the blank is determined according to the inner hole size of the forging.

[0011] As a further preferred embodiment of the present invention, in step 2, the outer circle of the blank The tolerance is controlled within 0~0.05mm, the inner hole size of the blank The tolerance of the middle and upper difference of the maximum inner hole step size of the forging is controlled within 0 to 0.05 mm.

[0012] As a further preference of the present invention, in step six, the lower end face of the tooth punch exceeds the working zone of the die, so that the blank flows downward along the working zone of the tooth punch and the die A during extrusion deformation. When the tooth punch moves downward, when the tooth punch does not contact the tube billet, the top end face of the tooth punch and the tooth punch pad are not in contact due to its own weight; when the tooth punch enters the inner hole of the tube billet, since the gap between the tooth punch and the inner hole of the tube billet is much smaller than the accumulated gap between the press and the die frame, in order to allow the tooth punch to smoothly pass through the inner hole of the tube billet, a circumferential and axial gap is set here. With this gap, the tooth punch can find the center and move up and down and shake circumferentially in the tooth punch transition sleeve.

[0013] As a further preferred embodiment of the present invention, in step six, a plurality of small holes for locking the punch sleeve are evenly arranged on the radial outer side of the upper locking nut, and the rods inserted into the small holes rotate the upper locking nut in clockwise and counterclockwise directions.

[0014] As a further preferred embodiment of the present invention, in step six, a plurality of small holes for locking the die sleeve and the lower die barrel are evenly arranged on the radial outer side of the lower locking nut, and the rods inserted into the small holes rotate the lower locking nut in clockwise and counterclockwise directions.

[0015] As a further preferred embodiment of the present invention, in step 6, a gap is provided between the end face of the tooth punch and the punch pad. The purpose of the gap is to make the tooth punch automatically find the center when entering the inner hole of the tube blank and when extruding the special-shaped internal spline, so that the tooth punch is not easy to break, because the gap between the press slide and the die frame makes the concentricity between the tooth punch and the die poor, and the tooth punch is very easy to break.

[0016] When the tooth punch moves downward, when the tooth punch does not contact the tube blank, the top end face of the tooth punch and the tooth punch pad are not in contact due to its own weight; when the tooth punch enters the inner hole of the tube blank, since the gap between the tooth punch and the inner hole of the tube blank is much smaller than the accumulated gap between the press and the die frame, in order to allow the tooth punch to pass through the inner hole of the tube blank smoothly, a circumferential and axial gap is set here. With this gap, the tooth punch can find the center, move up and down and shake circumferentially in the tooth punch transition sleeve.

[0017] As a further preferred embodiment of the present invention, in step six, a sealed opening is provided at the lower end face of the inner hole of die A, and a similar sealed opening is also provided at the inner hole opening of the upper end face of die B, so that the rear end faces of die A and die B fit tightly together after assembly, and material is not easily leaked during extrusion.

[0018] As a further preferred embodiment of the present invention, in step six, a gap is provided between the outer punch and the outer punch transition sleeve, and a gap is provided between the tooth punch and the tooth punch transition sleeve, and the gap is 1 mm.

[0019] As a further preferred embodiment of the present invention, in step six, a gap is provided between the outer punch and the punch sleeve, a gap is provided between the outer punch and the outer punch transition sleeve, a gap is provided between the tooth punch transition sleeve and the punch sleeve, and a gap is provided between the tooth punch and the tooth punch transition sleeve. The outer punch transition sleeve is installed in the punch sleeve with a gap of 0.03 to 0.07 mm on both sides, the outer punch is installed in the outer punch transition sleeve with a gap of 2 mm on both sides, the tooth punch transition sleeve is installed in the punch sleeve with a gap of 0.03 to 0.07 mm on both sides, and the tooth punch is installed in the tooth punch transition sleeve with a gap of 2 mm on both sides.

[0020] Beneficial effects: Compared with the prior art, the cold extrusion forming die for forming a tube blank with a special-shaped internal spline shaft described in the utility model has the following advantages:

[0021] (1) The upper die assembly and the forming die adopt die guide to ensure the concentricity of the forging after the upper and lower dies are formed;

[0022] (2) The mold structure adopts a three-layer prestressed structure with high mold strength. In addition, the middle ring is made of cemented carbide material, which ensures zero ejection after the forging is formed, ensuring the stability of the forging size and greatly improving the mold life;

[0023] (3) The products obtained by using this mold have high precision and low scrap rate, which reduces the overall cost and alleviates the pressure of investment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a full cross-sectional view of the blank after it is placed into the special-shaped internal spline cold extrusion die;

[0025] Figure 2 It is a partial enlarged picture;

[0026] Figure 3 This is a full cross-sectional view of the cold extrusion die for the special-shaped internal spline when forming the forging;

[0027] Figure 4 It is a schematic diagram of the structure of the blank;

[0028] Figure 5 Schematic diagram of the finished product after cold extrusion. DETAILED DESCRIPTION

[0029] The present invention will be further explained below in conjunction with the accompanying drawings.

[0030] like Figure 1As shown, the present invention discloses a cold extrusion forming die for forming a special-shaped internal spline shaft by forming a tube blank. The blank is placed in a concave mold cavity of the cold extrusion die for the special-shaped internal spline. The hydraulic press is used to move downward to drive the tooth punch 15 to extrude the blank to obtain the special-shaped internal spline shaft. The lower ejector rod 27 moves upward to eject the special-shaped internal spline shaft from the concave mold cavity. The cold extrusion die for the special-shaped internal spline comprises an upper die and a lower die coaxially mounted.

[0031] The upper die comprises: a punch sleeve 11, an outer punch transition sleeve 12, an outer punch 13, a tooth punch transition sleeve 14, a tooth punch 15, a punch pad 16, an upper die plate 17, an upper locking nut 18 and an upper die barrel 19, wherein the punch pad 16 is installed in the punch sleeve 11, and after the outer punch 13 is sleeved on the outer side of the tooth punch 15, the end of the tooth punch 15 is fixed in the punch sleeve 11 through the tooth punch transition sleeve 14, the end of the outer punch 13 is fixed on the punch sleeve 11 through the outer punch transition sleeve 12, the punch sleeve 11 is fixed on the upper die plate 17 through the upper die barrel 19, and the upper locking nut 18 provided on one side of the axial direction of the upper die barrel 19 is sleeved on the punch sleeve 11;

[0032] The lower die comprises: a coaxially arranged and sequentially close die A21, a die B23, and a die C24, a die sleeve 22 sleeved on the radially outer sides of the die A21, the die B23, and the die C24, the die sleeve 22 being fixed on a die pad 26 located on the axial end faces of the die sleeve 22 and the die C24 by a pressing plate 25, a lower die barrel 28 being sleeved on the radially outer sides of the die sleeve 22 and the die pad 26, a lower die barrel 28 being sleeved on the radially outer sides of the lower die barrel 28, a lower locking nut 20 being sleeved on the radially outer sides of the lower die barrel 28, the lower die barrel 28 being vertically fixed on a lower mold plate 29, and a lower ejector rod 27 being passed through the die pad 26 and the lower mold plate 29.

[0033] Example

[0034] Step 1: Cutting

[0035] According to the design, select the blank with the outer circle and inner hole size increased by 1mm of single-side machining allowance, and cut the steel pipe into the corresponding length with a circular saw according to the cutting length;

[0036] Step 2: Turning

[0037] According to the size requirements of the blank, inner hole The length dimension L is turned in place, according to the weight C of the forging, and the length L of the billet is based on the outer diameter of the billet. and inner hole get:

[0038]

[0039] The deformation of the blank is controlled within 60%, and the punch unit pressure does not exceed 2500Mpa. The tolerance is controlled within 0~0.05mm, the inner hole size of the blank The tolerance of the maximum inner hole step size of the forging is controlled within 0~0.05mm;

[0040] Step 3: Spheroidizing annealing

[0041] The blank after turning is placed in an annealing furnace and heated to 730℃~740℃ for 2h~3h insulation treatment, and then slowly cooled to 650℃ at a speed of less than 20℃ / h and taken out of the furnace;

[0042] Step 4: Sandblasting

[0043] The outer circle and inner hole of the spheroidized billet are sandblasted to remove the oxides produced by spheroidizing annealing; tiny concave and convex textures can be formed on the billet surface to increase the surface area of ​​the billet and increase the area of ​​the subsequent film.

[0044] Step 5: Surface treatment

[0045] The sandblasted blank is placed in a phosphorus saponification pretreatment solution to treat the surface of the blank with a phosphorus saponification film, which reduces the friction when the metal flows and makes forging easier.

[0046] Step 6: Extruding special-shaped internal splines

[0047] The downward movement of the hydraulic press drives the outer punch 13 and the tooth punch 15 to move downward together through the press slider. The tooth punch 15 first passes through the inner hole of the blank, and then the outer punch 13 enters the die core 233 of the die B until the outer punch 13 contacts the end face of the blank. At this time, the lower end face of the tooth punch 15 exceeds the die core 233 of the die B, so that the blank flows downward along the working belt of the tooth punch 15 and the die A21 during extrusion deformation. The outer punch 13 pushes the blank to continue to move downward, and the blank is formed into a special-shaped internal spline through the die core 233 of the die B and the tooth punch 15. The tooth punch 15 will move downward with the blank until it is extruded to the required length of the forging to obtain a finished product. The press slide moves back upward, driving the outer punch 13 and the tooth punch 15 to move upward together, so that the tooth punch 15 completely leaves the inner hole of the forging and returns to the upper limit position of the press slide. The machine tool push rod pushes the lower ejector rod 27 to move upward to push the forging out of the die, and the forging is manually taken out and placed in the material frame.

[0048] The die A21 includes a die A shell 211, a die A center ring 212 and a die A core 213. The die A shell 211, the die A center ring 212 and the die A core 213 all adopt a large press fit interference fit. A guide section is provided at the inner hole mouth to facilitate the external punch to smoothly enter the inner hole of the die. The die A21 mainly serves to store the blank and guide the external punch. The inner hole diameter is about 0.1mm larger than the blank diameter, which facilitates the blank to be placed in the die cavity. A sealed opening 100 is provided at the lower end face of the inner hole of the die A21, and the same sealed opening 100 is also provided at the inner hole mouth of the upper end face of the die B23, so that the die A21 and the die B23 are closely fitted at the rear end face after assembly, and it is not easy to leak during the extrusion process.

[0049] The die B23 adopts a three-layer stress sleeve structure, including a die B shell 231, a die B middle ring 232 and a die B core 233. The die B shell 231, the die B middle ring 232 and the die B core 233 all adopt a large press fit interference fit, and the die B core 233 is made of cemented carbide material with high strength and good wear resistance. The mouth size of the die B23 is the same as the inner hole size of the die A21. The die entry angle, working belt and hollow section are provided below. The inner hole diameter of this working belt is the outer circle size of the forging. The material will simultaneously form the special-shaped internal spline and outer circle along this working belt and the tooth punch. The hollow section is 0.4-0.5mm larger than the inner hole diameter of the working belt, which can reduce the forming force.

[0050] The die C24 adopts a two-layer stress sleeve structure, including a die C241 shell and a die C core 242. Both the die C shell 241 and the die C core 242 adopt a large press fit interference fit, and the inner hole size is the same as the size of the hollow section of the die B23.

[0051] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable technicians familiar with the technical field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A cold extrusion die for forming a special-shaped internal spline shaft of a tube blank, characterized by: It includes coaxially mounted upper and lower dies; The upper die comprises: a punch sleeve (11), an outer punch transition sleeve (12), an outer punch (13), a tooth punch transition sleeve (14), a tooth punch (15), a punch pad (16), an upper die plate (17), an upper locking nut (18) and an upper die barrel (19); the punch pad (16) is installed in the punch sleeve (11); after the outer punch (13) is sleeved on the outer side of the tooth punch (15), the end of the tooth punch (15) is fixed in the punch sleeve (11) through the tooth punch transition sleeve (14); the end of the outer punch (13) is fixed on the punch sleeve (11) through the outer punch transition sleeve (12); the punch sleeve (11) is fixed on the upper die plate (17) through the upper die barrel (19); and the upper locking nut (18) provided on one side of the axial direction of the upper die barrel (19) is sleeved on the punch sleeve (11); The lower die comprises: a die A (21), a die B (23), and a die C (24) which are coaxially arranged and closely adjacent to each other, a die sleeve (22) which is sleeved on the radially outer sides of the die A (21), the die B (23), and the die C (24), the die sleeve (22) being fixed on a die pad (26) located on the axial end faces of the die sleeve (22) and the die C (24) by a pressing plate (25), a lower die barrel (28) being sleeved on the radially outer sides of the die sleeve (22) and the die pad (26), a lower locking nut (20) being sleeved on the radially outer sides of the lower die barrel (28), the lower die barrel (28) being vertically fixed on a lower mold plate (29), and a lower ejector rod (27) being passed through the die pad (26) and the lower mold plate (29).

2. The cold extrusion forming die for forming a special-shaped internal spline shaft of a tube blank according to claim 1, characterized in that: A gap is provided between the end surface of the tooth punch (15) and the punch pad (16).

3. The cold extrusion forming die for forming a special-shaped internal spline shaft of a tube blank according to claim 2, characterized in that: A plurality of small holes for locking the punch sleeve (11) are evenly arranged on the radial outer side of the upper locking nut (18), and the rods inserted into the small holes rotate the upper locking nut (18) in clockwise and counterclockwise directions.

4. The cold extrusion forming die for forming a special-shaped internal spline shaft of a tube blank according to claim 1, characterized in that: A plurality of small holes for locking the die sleeve (22) and the lower die barrel (28) are evenly arranged on the radial outer side of the lower locking nut (20), and rods inserted into the small holes rotate the lower locking nut (20) in clockwise and counterclockwise directions.

5. The cold extrusion forming die for forming a special-shaped internal spline shaft of a tube blank according to claim 1, characterized in that: The lower end surface of the inner hole of the die A (21) is provided with a sealed opening (100), and the inner hole opening of the upper end surface of the die B (23) is also provided with a similar sealed opening (100).

6. The cold extrusion forming die for forming a special-shaped internal spline shaft of a tube blank according to claim 1, characterized in that: A gap is provided between the outer punch (13) and the outer punch transition sleeve (12), and a gap is provided between the tooth punch (15) and the tooth punch transition sleeve (14).

7. The cold extrusion forming die for forming a special-shaped internal spline shaft into a tube blank according to claim 1, characterized in that: A gap is provided between the outer punch (13) and the punch sleeve (11), a gap is provided between the outer punch (13) and the outer punch transition sleeve (12), a gap is provided between the tooth punch transition sleeve (14) and the punch sleeve (11), and a gap is provided between the tooth punch (15) and the tooth punch transition sleeve (14).

8. The cold extrusion forming die for forming a special-shaped internal spline shaft into a tube blank according to claim 1, characterized in that: The upper mold plate (17) is connected to the oil press.

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